1. Field of the Invention
This invention relates generally to cutting implements, specifically to a scalpel with a rotary depth guard.
2. Prior Art
A typical surgical scalpel includes an extremely sharp, straight cutting blade, made of surgical-grade stainless steel, affixed to the end of a handle. The vast majority of scalpels are simple variations on the same basic shape. In use, the blade is pressed into the tissue to be cut, then pulled along the tissue to make an incision. As the blade slides pass tissue wet with body fluids, it tends to drag the tissue along because of surface adhesion. As a result, the tissue is distorted and cut slightly unevenly. The depth of the incision may also be uneven along its length, depending on the skill of the surgeon. Uneven incisions cause uneven pulling or bunching of the tissue during healing, so that excessive scaring may result. This is an acute problem for plastic and reconstructive surgeons, who are particularly concerned about minimizing scare tissue. Some surgical procedures, such as flap transfer, hair transplants, skin gratfs, and corneal incisions, require incisions at known and even depths--a precision that conventional scalpels cannot provide.
Surface adhesion or dragging can be minimized by using a rotary disc cutting blade that rolls along the tissue. Such rotary cutting implements have been extensively applied in a variety of uses, such as cutting cloth, paper, and food substances. A well known example is the rotary pizza knife that cuts through a pizza without dragging the cheese, similar to that shown in U.S. Pat. No. 630,094 to Noble (1899).
U.S. Pat. No. 1,574,819 to Jezler (1926) shows an animal skinning knife with a toothed-wheel that serves as a safety guard and guide for the cutting disc. The tips of the teeth extend beyond the perimeter of the cutting disc to allow a very shallow cutting depth. In use, the skinning knife is forced against the point of union between the hide and the flesh of a carcass to separate them. The bumpy rolling motion of the toothed-wheel causes the knife move up and down as it is pulled along, so that the cuts are uneven in depth.
Rotary cutting implements have also been specifically adapted for use in surgery. U.S. Pat. Nos. 756,213 to Connell (1904) and 4,791,928 to Berke et al. (1988) each shows a scalpel with a rotary disc blade. However, they include no provision for controlling the cutting depth, so that incisions of uneven depth can still be easily made. Furthermore, when the desired cutting depth is very shallow, and the surgical field is very wet and slippery, there is not enough friction between the blade and the tissue for properly rotating the blade. As a result, the rotary blade may be dragged along the tissue like a straight knife and produce an uneven incision.
Two rotatable blade scalpels are shown in U.S. Pat. No. 5,342,377 to Lazerson (1994) and the Jun. 15, 1994 issue of Ocular Surgery News. Each of these scalpels has a blade pivoted about an axis that lies on the plane thereof, so that the blades are rotatable for changing the direction of the cutting line with respect to the axis of the handle, i.e., these blades are primarily used for cutting circles. They do not rotate like wheels, so that they drag along the tissue in the same way as fixed blades. Furthermore, they have no provision for controlling penetration, so that they will produce incisions with uneven depths.